This invention is related to a device that will provide the stretching and molding of can bodies, more specifically for cans manufactured with tinplate and destined for food packaging, through which, and due to its special building and working features, the stretching and molding and consequent growth of the diameter of the can body, is obtained by an extremely practical and efficient way, by means of one single operation, thus excluding the need for equipment with great complexity and high cost as other methods known and used for the same purposes.
The expansion of this kind of cans, always seeking for more raw material savings and cost reduction on metal packaging, is now obtained by means of extremely complex expanding devices, normally made out of rules of cleats, rulers or tongs, which are introduced into the can body to be expanded and, when driven, said devices open or dilate, projecting themselves against the inner sidewall of the can body, causing its expansion and subsequent diameter growth relative to the ends that will be closed by lids by seaming operation.
This procedure obtained by means of these known expanding devices, through which only the expansion of the can body is obtained, although satisfying their purposes to a certain extent, besides their complex building form and high cost, they have their function restricted merely to the can diameter increase, in order to afford higher volumetric capacity of the can body.
The stretching and molding device for can bodies in reference, comes to solve that problem in a much practical and definitive way, substantially differentiated from the known devices by both, its building and its operational form, essentially comprised by a rigid and solid forming block, generically cylindrical, which constitutes at the same time, the stretching or molding element, which presents the larger area of its body with a bigger diameter corresponding to the inner diameter of the can body to be obtained by stretching and having a conic section that is topped by a short cylindrical section which diameter is smaller than the one of the bottom portion of the forming block.
This forming block, that constitutes an essential part of the stretching and molding device, either penetrates or receives under pressure the cylindrical body of the can, that has originally a smaller diameter, simply rolled and electrically welded, thus allowing its stretching and formation, molding itself to the outer surface of the forming block and having the greatest part of its body augmented in diameter relative to the diameter of the upper end, that remains with its original diameter, forming what is known as neck-in, all that through a single operation, which is complemented by tooling applied to the upper and lower parts of the assembly, through which, on the same stretching and molding operation, flanges are obtained at the ends of the stretched and formed can body, destined to allow the application of the forming disks for bottom and top can lids on a subsequent seaming operation.
The stretched and formed can body by means of said device, still will might have its upper end of smaller diameter forming the can top provided with a plump cord upturned outwards, by the use of a complementary tool and operation, to allow the can to receive a non seamed metal lid and be closed thereby, said metal lid being provided with sealing gaskets and vacuum closed, of the easy-open kind.